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low level problem
i purchased this coach with the right rear goes down after 5 mins of turning the engine off. so here are the steps that did
bought new Norgen 5 way valves and 3 way for the rear ..
Had local shop install valves, all great at shop
3 miles from shop rear drop while driving
Stopped bus and turn everything off, started bus up all fine
againDrove about 2 miles (home now) bus leaning
Let bus sit over night after dumping all air
Ran shop air to bus, bus came up to normal height (key off)
bus sat prefect 24hrsStarted bus up all good, turn bus off after 5 mins, Bus
leaning to right againStarted bus up all good , turn bus off , turn key back on
(not starting) all good after 2 hrs. turn swtich offThe next day right rear down, hook up shop air nothing
happens, turn key on not starting. up
she comes!I am guess my problem is the right rear part of the 5 stack valve in the
fwd lowers drivers compartment!Your thoughts?
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13 Replies
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You have a problem. I am not talking about the leans. I am talking about something that is making the coach act in a most unusual manner. It may be serious, it may be simple, but your first action has to be to verify the suspension does what it is told by you at the controls.
First, if the coach has another suspension control system like an aftermarket HWH that was installed by Marathon, disable it. That should leave you with a round knob on a 4 position selector and a rocker switch to control all suspension operation.
With the coach lowered or at any odd position, and the rotary switch in the road or driving position you should be able to start the coach, air it up and the coach should go to and remain at the correct driving height. You said it drops in the rear so that problem needs to be isolated.
If with the supplemental suspension system control disabled it functions correctly the problem is in that control. If the problem persists it could be a number of things uncluding multiple problems simultaneously impacting the system, such as water in the system combined with leaks.
Rather than trying to over analyze it start with simplifying the problem by using only the Prevost installed controls and see what happens. I get really concerned on older coaches, especially those that have had non=Prevost mechanics work on them, and especially those whose history is unknown.
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The only controls i have are the factory installed by prevost. Everything seems to be working normal as long as the key is on (at this pont)! the only thing i can see in the print(s) that has wires /air valve is the 5 stack Norgen valves in the lower drivers panel! everything on the control panel works as it should, when the key is on . Hmm. Maybe Piece of dirt got inside when they changed the 5 way and 3 way valves.
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My guess, Dave sounds like it’s electrical somehow. Have you killed main switches back by engine and see if no voltage is getting to controls after airing up.? Mine will sink in back after about a week if sitting in barn and this is after spending several thousand at Prevost replacing 5 way, 3 way, valves, fittings and who knows what else. Of course Prevost service is the only place I would take it to on air issues unless you know somebody that is familiar with systems.
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Dave,
If you only have the Prevost installed level low controls it should only work when the key is on. It should automatically shut air in the 3 suspensions as soon as the key is off.
Without knowing the history of the coach the only way you can isolate and chase problems is to start verifying things do in fact work as designed, but you alread said they do not because you said the rear dropped while driving. So we know something is screwed up, but to what extent is as yet unknown.
I worked on a coach that dropped in the LH rear when the coach was in the driving or road position. I traced everything from the origin, and found the center coil was getting power and the valve was opening because that air line was getting air. The 5 port Norgren in the rear was getting air, but the air which should have gone through the ride height valve and the 5 port Norgren was not passing through the Norgren into the air bags on that side.
When we opened the Norgren we found the plunger was water logged and internal corrosion had caused the valve to bind up and not open the air path as intended. Since you have new valves you might be able to rule that problem out, but despite the new valves I would follow the air to find out why the rear drops. It is time consuming but I do not know an alternative to verifying everything works as intended.
One thing I would question is if you have the system that locks air in the air bags via the 5 port valves, or do you have the early Prevost logic that dumps tag axle air (via the three port valve between the drive and tag) when aux air pressure drops. Further, I would actually see if a mechanic has every mixed up air lines and hooked them to different ports, or if someone got creative and decided they knew how to make it work better than the Prevost engineers.
Under normal conditions tracing air suspension system issues is normally easy, but if the system gets water in it, or if a previous mechanic swapped stuff around or if a part failed like a solenoid coil on the manifold it may require some study of the system.
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We had a similar problem late year. Jon was very helpful in helping me trouble shoot the problem(s). after a few days at Prevost Nashville and the problem not resolved we went to Jeff with ETLC. All was resolved and holding steady. Worth considering if you cannot resolve. Thanks to both Jon and Jeff.
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Early Sunday morning i took her out for a short drive! i drove a mile and stopped and looked all fine, drove 2 more miles bus was starting to lean to the right, drive one more mile bus all the way down . turned Bus off, started her back up, up she comes ! drove her home and parked her! Ran Back to the rt rear and i could hear air leaking and she was dropping fast ! Monday morning went and made another appt to have it looked at. i will let you all know what happens!
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under 5 solenoid control valves small about 1/4 od easy to miss align Rear air leak could well be a poorly attached (at fitting) air line came off. Didn’t see where you are but it would be good if someone was close with a knowledge of Prevost system that could help you. Not really much to it. Use prevostcar.com web site for help or see articles section of this board to help you understand more.. If nothing else it can provide you with info to judge how good your mechanic is. your ser# or prevost web site will be last letter of serial # plus last 4 numbers. for a 95 coach should be R then last 4 numbers= unit number Example mine is W 6553 FWIW Bob
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Should be on coach leveling system (mechanical actuwated) Things to ck Did rod come loose to mechanical leveling valve? Line come loose etc.
? 2 leveling valves on rear one on front. Good luck!
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Dave…………who are you having look at the coach and what exactly is their depth of experience on resolving an issue with a Prevost suspension system? It sounds completely unlike any problem that could ever be anticipated on a Prevost system that has been unmodified. If someone previously screwed with it, something as simple as reversing a couple of air lines you could be in worse trouble than you are notw. And you are in trouble.
I don’t want to sound pessimistic about your chances of success, but a lot of owners have found if a mechanic does not understand the system, does not work from the system pneumatic diagrams, does not methodically follow the system, starting with the electric signals to the solenoid manifold and then the air from that manifold to the vatious Norgren valves not only can you expect your coach to suffer, you can plan on having your wallet suffer before this is fixed.
My first question to the mechanic would be to ask if the coach has the current pneumatic system logic in which the accessory air can go to zero and the coach suspension retains its air, or if it has the previous system logic in which the accessory system had to be at 35 PSI or above to prevent the tag axle Norgren valves from dumping air. If the mechanic can not answer that question go to one that can. Your coach is right at the age when the system logic was changed.
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Well here we go! I purchased New 3&5 way valves for the ones i already replaced. After tracing lines looking a prints debating the problem. I think i am finally fixed ! holly molly there is a god! after fixing some small air leaks here and there the bus wouldnt lean hard to the right to save my life while at the shop . so we took off the leveling valve and started to mess with it on the bench.We hooked air to it and it worked some times . R&R valve went for a test drive,all is good! been sitting for 5hrs ! All good!
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Way to go Dave. Congrats. -
Thanks
Well after 4 days the right rear dropped 1 inch .the front and left side still rock solid . i guess i will call it good? thanks all for the advise!
does any one know if the leveling valve on the left is the same as the right? -
The Norgren valves are the same left and right, and the ride height valves are the same left and right.
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